Yea I agree he is some what useful... but ever since I read that part whereby he challenged Luffy and threatened to leave the crew, I start to dislike him. Then, after the CP9 incident, he still think the crew will beg him to return to the crew. I totally hate him from then onwards.

Besides, I think Luffy can smash up any boat/ship with his giant arms. So, they dont really need any sniper to do the job.
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Unless, Luffy cant even control his arms...